1—Field of Invention
The present invention is in the field of medicine, particularly in relation to nasogastric catheter placement.
2—Description of the Prior Art
Nasogastric intubation has been practiced for a very long time. This has been always a difficult and uncomfortable procedure. The tip of the nasogastric tube frequently causes injury to the nasal passage mucosa. This is because of the anatomical configuration of human nasal passage which includes a sharp curve at the nasopharynx. There are various types of nasogastric tubes from simple ones to the recently introduced sump drain nasogastric tubes. A problem that is always present with these tubes is their rigidity vs. maneuverability. If the catheter is rigid enough to be able to be maneuvered and pushed through the nasopharynx and hypopharynx into the esophagus, it may well injure the mucosa by it's tip, and if it is made of very soft material it may not be easily maneuvered and needs a rigid stylet to
assist during insertion, but these will collapse their internal lumen if connected to suction because their wall is so soft and pliable and are suitable only for purpose of feeding not for suctioning. Examples of the first type of tubes are the currently used nasogastric suction catheters and examples of the second group include the current enteric feeding tubes.
In order to overcome these shortcomings, several inventions have been disclosed before.
For the rigid catheters a lumen seeking nasogastric tube with a flexible tip was disclosed by Klingenstein (U.S. Pat. No. 5,700,252, December, 1997). Another prior art is a stylet to help the tube negotiating the nasopharyngeal curve (Micek, U.S. Pat. No. 4,747,827, May, 1988).
For the softer tubes disclosures includes multiple type of conduit tubes to push the feeding tube through the nasopharynx or hypopharynx all the way to the stomach and then removing the conduit (Okada, U.S. Pat. No. 4,887,997, December 1989) or stylets to temporarily stiffen the tube (Etheredge, U.S. Pat. No. 4,938,746, March 1988; Beal, U.S. Pat. No. 4,257,421, March 1981). The conduit proposed by Okada proposed a conduit that it is to be inserted all the way to the stomach and then after placement of the nasogastric tube that conduit is removed via a special separator. This is different to the current disclosed nasopharyngeal sheath because the main difficulty and concern for mucosal injury still exists with the Okada's conduit. It is mainly targeted for placing the very soft feeding tubes, which are not suitable for nasogastric suctioning. Kwak (U.S. Pat. No. 4,175,564) proposes to insert the nasogastric tube through the nose and pull it through the mouth then a guide to be inserted through the mouth into the esophagus and the nasogastric tube will pass through it into the esophagus. This technique still requires passing the nasogastric tube through the nasopharyngeal airway with potential for causing injury. There are also innovative approaches including swallowing an absorbable string to guide the catheter during insertion (Peters, U.S. Pat. No. 201,556, February 1994).The shape of human nasopharynx is such that it has a sharp curve at its passage to pharynx and subsequently hypopharynx. Passing tubes and catheters often causes injury to the mucosa and bleeding of the posterior wall of the nasopharynx. Tubes that have inherent curve on the other hand can easily pass through this curve; examples are the current nasopharyngeal airway catheters. The same problem exits even when a patient is endotracheally intubated. Placing a nasogastric tube can still be very traumatic. Also, in patients who have problems with their coagulation, conventional nasopharyngeal intubation can potentially cause significant bleeding because of the mucosal injury.
It is to be said that the disclosed nasopharyngeal sheath is different comparing to the current commercially simple nasopharyngeal airway catheters or their various modifications like the ones described by Downing or Linder among others (U.S. Pat. No. 4,821,715 which issued on Apr. 18, 1989 to Michael V. Downing, U.S. Pat. No. 5,664,567 which issued on Sep. 9, 1997 to Gerald S. Linder and in U.S. Pat. No. 5,692,506 which issued on Dec. 2, 1997 also to Gerald S. Linder). The scopes of function of the two are completely different. The curve of the nasopharyngeal airway catheter is such that it places the tip of the catheter as close to the tracheal opening as possible and all the modifications mentioned above aim to better deliver oxygen to the patient, while the disclosed sheath has a wider curve to be able to point more posteriorly towards the esophagus rather than the trachea which is located more anteriorly. Also none of the current nasopharyngeal airways have the tear-off mechanism or the pulling rings.
The disclosed invention uses a curved rubber tube to secure a safe pathway for the nasogastric tube into the hypopharynx. Once there, the tip of the rubber sheath positions the nasogastric tube tip above the esophageal aperture, therefore the catheter can be easily pushed into the esophagus. For further understanding and appreciation of the invention and its advantages reference is made to the Drawings and Detailed Description below.